967
FXUS63 KBIS 171135
AFDBIS
Area Forecast Discussion
National Weather Service Bismarck ND
635 AM CDT Sat Mar 17 2018
.UPDATE...
Issued at 625 AM CDT Sat Mar 17 2018
As mid and high level clouds retreat to the north, satellite
loops show a large stratus layer remaining across western North
Dakota. This will eventually erode as h850 west warm advection
winds develop late this morning and afternoon. But these clouds
may remain a bit longer into the early afternoon. Otherwise the
current forecast looks ok.
&&
.SHORT TERM...(Today and tonight)
Issued at 246 AM CDT Sat Mar 17 2018
The short term will be a relatively quiet period compared to the
extended. Early morning clouds across the west will gradually
decrease and move east and north. Highs Saturday will be in the
lower 30s north to near 40 southwest. Model consensus for this has
the upper low over Nebraska moving east allowing an h500 ridge to
build into the northern plains Saturday afternoon and night.
The rest of this morning will continue to monitor for some
residual light Snow southwest along with some patchy fog which
will diminish and end by late morning.
.LONG TERM...(Sunday through Friday)
Issued at 246 AM CDT Sat Mar 17 2018
The focus in the extended will be the Sunday and Monday period.
A somewhat dispersed h500 low over the northwest US on Saturday
will break down and send several shortwaves in a weakly split
flow into the northern plains. With temperatures in the critical
threshold of mid 30s there will be rain and snow with at least a
touch of freezing drizzle Sunday afternoon and evening. The GFS
brings a vort center into southwest North Dakota Sunday afternoon
and evening which should develop support an area of precipitation
oriented northeast to southwest across western North dakota. The
evening hours on Sunday will see a period where there is support
for banded precipitation. Frontogenesis and fairly steep mid
level lapse rates will support this. So the best period of
precipitation potential will be late Sunday afternoon and Sunday
night. We have aligned the higher precipitation amounts during
this period. This will be followed by decreasing pops and qpf on
Monday.
There continues to be some uncertainty in the snow amounts as
temperatures will initially support both snow and rain. The
probabilistic snow amounts suggest a moderate threshold for 4
inches over central North Dakota for Sunday night and Monday.
With this in mind our approach will be to issue a special weather
statement detailing the snow potential and highlight mainly travel
hazards.
Tuesday through Thursday will see a building ridge across the
northern plains which will suppress precipitation but another
rather robust negatively tilted upper low is forecast to move from
the northwest US into the upper plains by Friday. This will
provide another opportunity for precipitation, both rain and snow.
&&
.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 625 AM CDT Sat Mar 17 2018
Hazards to aviation for the 12z TAFs include MVFR conditions due
to stratus clouds. The stratus will gradually erode during the
day but return overnight tonight.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...WAA
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...WAA